Cylinder head gasket

ABSTRACT

A cylinder head gasket 1 comprises a pair of gasket baseplates 3 having a combustion chamber opening 3A formed therein, and a spacer 4 disposed around a cylinder bore 2 to surround it in an endless manner and held sandwiched between the pair of gasket baseplates 3. A full bead 3a and a half bead 3b are formed on each gasket baseplate in a region overlapped by the spacer 4, and the spacer as well as the full bead and the half bead are continuously held sandwiched between a cylinder head 5 and a cylinder block 6 along the circumference of the cylinder bore. The spacer allows the full bead and the half bead to be brought into abutment against the mating member under a high surface pressure and over a relatively extensive area of contact, whereby a good sealing performance is obtained in the presence of a gross porosity in the casting or flaw on the mating adjoined surface.

TECHNICAL FIELD

The invention relates to an improvement of a cylinder head gasket of anengine.

BACKGROUND OF THE INVENTION

A cylinder head gasket is known in the art comprising a pair of gasketbaseplates held sandwiched between a cylinder head and a cylinder blockand having a combustion opening formed therein in alignment with acylinder bore, a spacer disposed around the cylinder bore to surround itin an endless manner and held sandwiched between the pair of gasketbaseplates and a full bead and/or half bead formed at a suitablelocation or locations on the gasket baseplates (Japanese Laid-OpenUtility Model Application No. 71,865/1992 and Japanese Laid-Open PatentApplication No. 165,167/1992).

In the prior art, when only gasket baseplates are provided which areformed with a full bead and a half bead, they are readily susceptible tothe influence of any blowhole in the casting or flaw on mating adjoinedsurface, causing likelihood that the sealing performance becomesdegraded.

DISCLOSURE OF THE INVENTION

In view of the foregoing, the invention provides a cylinder head gasketwhich assures and maintains a good sealing performance in the presenceof any blowhole in the casting or flaw on the mating adjoined surface.

Specifically, in accordance with the invention, there is provided acylinder head gasket comprising a pair of gasket baseplates heldsandwiched between a cylinder head and a cylinder block and having acombustion opening formed therein in alignment with a cylinder bore, aspacer disposed around the cylinder bore to surround it in an endlessmanner and held sandwiched between the pair of gasket baseplates, and afull bead and a half bead formed on each of the pair of gasketbaseplates in a region overlapped by the spacer, the spacer as well asthe full bead and the half bead on the respective gasket baseplatesbeing continuously held sandwiched between the cylinder head and thecylinder block along the circumference of the cylinder bore.

With the described arrangement, the full bead and the half bead on eachof the gasket baseplates disposed around the combustion chamber openingare held sandwiched between the cylinder head and the cylinder block,and the spacer is interposed therebetween in such region. This allowsthe full bead and the half bead to abut against the mating member undera high surface pressure and over an increased area of contact, withconsequence that they are less susceptible to the influence of any grossporosity in the casting or flaw on the mating adjoined surface, thusenabling a good sealing performance to be secured.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal section of a first embodiment of the invention;

FIG. 2 is a plan view of cylinder head gasket 1 shown in FIG. 1;

FIG. 3 is a cross section, to an enlarged scale, of a pertinent portionshown in FIG. 1; and

FIG. 4 is a longitudinal section of a second embodiment of theinvention.

BEST MODES FOR CARRYING OUT THE INVENTION

The invention will now be described below with reference to anembodiment applied to a linear four cylinder engine.

Referring to FIGS. 1 and 2, a cylinder head gasket 1 comprises a pair ofgasket baseplates 2 having four combustion chamber openings 3A formedtherein in alignment with respective cylinder bores 2 (see FIG. 1) and aspacer 4 disposed between the pair of gasket baseplates 3 to be heldsandwiched therebetween.

The spacer 4 is disposed around each cylinder bore 2 to surround it inan endless manner. However, in the embodiment shown, because a spacingbetween the cylinder bores 2, and hence, between the combustion openings3A is reduced, four spacers 4 are integrally connected together betweenadjacent combustion openings 3A so as to be continuous to each other.Where there is an increased spacing between the combustion openings 3A,it will be obviously seen that the four spacers may be separate fromeach other.

In a region overlapped by the spacer 4, each gasket baseplate is formedwith a full bead 3a and a half bead 3b, each of which surrounds therespective combustion opening 3A and is formed as a projection from thespacer 4. The full bead 3a and the half bead 3b are formed in thesequence named as viewed in a direction from the combustion openings tothe outside thereof.

SUS 301-H having a thickness of 0.20 mm, for example, may be used foreach of the gasket baseplates 3. Preferably, its opposite surfaces arecoated with NBR layers 3c, as shown in FIG. 3. For the spacer 4, SUS 304having a thickness of 0.08 mm may be used. However, it should beunderstood that the thickness and the material of the gasket baseplate 3may be suitably selected depending on the variety of an engine to whichit is applied.

As shown in FIG. 1, the cylinder head gasket 1 is interposed between acylinder head 5 and a cylinder block 6 of the engine and is heldsandwiched therebetween to provide a sealing between the both byintegrally connecting the cylinder head 5 and the cylinder block 6 by aclamping bolt 7.

In this example, the spacer 4 as well as the full bead 3a and the halfbead 3b on the respective gasket baseplates 3 are continuously heldsandwiched between the cylinder head 5 and the cylinder block 6 alongthe circumference of the cylinder bore 2, thus providing a safeguardpreventing a circum-ferential continuity from being interrupted orpreventing part of the half bead 3b which is located on the outer sidefrom being trapped into cooling water passages 5a, 6a formed in theadjoining surfaces of the cylinder head 5 and/or the cylinder block 6 toprevent such part from being held sandwiched.

In the embodiment shown, the cylinder head 5 and the cylinder block 6are formed as aluminum die-cast open decked blocks, and the coolingwater passages 5a, 6a are formed in the adjoining surfaces of thecylinder head 5 and the cylinder block 6, respectively, so as tosurround the four combustion openings 3A in an integral manner at alocation on the outside of the outermost half bead 3b.

With the described construction, each of the combustion chamber openings3A can be surrounded by the full bead 3a and the half bead 3b in anendless manner. In addition, since the spacer 4 is disposed in theregion where the full bead 3a and the half bead 3b are provided, thefull bead 3a and the half bead 3b can be brought into abutment againstthe cylinder head 5 and the cylinder block 6 under a high surfacepressure and over a relatively extensive area of contact.

As a consequence, it is less susceptible to the influence of any grossporosity in the casting or flaw on the adjoining surfaces of thecylinder head 5 and the cylinder block 6, allowing a good sealingperformance to be secured and maintained.

FIG. 4 shows another embodiment of the invention in which a reinforcingplate 11 of a reduced thickness than the spacer 4 is disposed on theoutside of the spacer 4 of the first embodiment. The reinforcing plate11 is held sandwiched between the pair of gasket baseplates 3, and adifference in the thickness between the reinforcing plate 11 and thespacer 4 in this embodiment is chosen to be equal to the thickness ofthe spacer 4 in the first embodiment.

Again, a similar function and effect is achieved as in the firstembodiment, while allowing the rigidity of the entire cylinder headgasket 1 to be enhanced.

INDUSTRIAL APPLICABILITY

As described, according to the invention, the gasket is less susceptibleto the influence of any gross porosity in the casting or flaw on themating adjoined surfaces, permitting a good sealing performance to besecured.

What is claimed is:
 1. A cylinder head gasket including a pair of gasketbaseplates held sandwiched between a cylinder head and a cylinder blockand having a combustion opening formed therein in alignment with acylinder bore, a spacer disposed around the cylinder bore to surroundthe cylinder bore in an endless manner, said spacer being heldsandwiched between said pair of gasket baseplates, and a full bead and ahalf bead formed on each of said pair of gasket baseplates in a regionoverlapped by said spacer,wherein the improvement comprises said fullbead and said half bead extending continuously, completely around thecircumference of the cylinder bore, the spacer as well as the full beadand the half bead on each gasket baseplate being continuously heldsandwiched between the cylinder head and the cylinder block along thecircumference of the cylinder bore; and a reinforcing plate of a reducedthickness which is less than the thickness of said spacer, saidreinforcing plate being disposed outboard of said spacer, saidreinforcing plate being held sandwiched between said pair of gasketbaseplates.
 2. In combination, a cylinder head, a cylinder blockconnected to said cylinder head and having a cylinder bore, and acylinder head gasket, said cylinder head gasket including:a pair ofgasket baseplates sandwiched between said cylinder head and saidcylinder block, said gasket baseplates including a combustion openingformed therein in alignment with said cylinder bore; a spacer disposedaround said cylinder bore to surround said cylinder bore in an endlessmanner, said spacer being held sandwiched between said pair of gasketbaseplates, a full bead and a half bead being formed on each of saidpair of gasket baseplates in a region overlapped by said spacer, saidfull bead and half bead extending continuously, completely around thecircumference of said cylinder bore, said spacer and said full bead andhalf bead on each gasket baseplate being held sandwiched between saidcylinder head and said cylinder block continuously along thecircumference of the cylinder bore, at least one of said cylinder headand said cylinder block being formed as an open deck formed with acooling water passage which surrounds said spacer and said full bead andhalf bead on each said gasket baseplate.
 3. A combination according toclaim 2, in which said cylinder head gasket includes a reinforcing plateof a reduced thickness which is less than the thickness of said spacer,said reinforcing plate being disposed outwardly of said spacer, saidreinforcing plate being held sandwiched between said pair of gasketbaseplates.
 4. A combination according to claim 2, wherein said halfbead is positioned radially outwardly of said full bead.
 5. A cylinderhead gasket according to claim 2, wherein said full bead is directlyadjacent a combustion opening and has a central portion extendingaxially away from said spacer.
 6. A cylinder head gasket according toclaim 5, wherein a said half bead extends axially away from said spacerand is positioned radially outwardly from said full bead.
 7. A cylinderhead gasket including a pair of gasket baseplates held sandwichedbetween a cylinder head and a cylinder block and having a combustionopening formed therein in alignment with a cylinder bore, a spacerdisposed around the cylinder bore to surround the cylinder bore in anendless manner, said spacer being held sandwiched between said pair ofgasket baseplates, and a full bead and a half bead formed on each ofsaid pair of gasket baseplates in a region overlapped by saidspacer,wherein the improvement comprises said full bead and said halfbead extending continuously, completely around the circumference of thecylinder bore, the spacer as well as the full bead and the half bead oneach gasket baseplate being continuously held sandwiched between thecylinder head and the cylinder block along the circumference of thecylinder bore, said full bead being directly adjacent the combustionopening and having a central portion extending axially away from saidspacer.
 8. A cylinder head gasket according to claim 7, wherein saidhalf bead extends axially away from said spacer and is positionedradially outwardly from said full bead.
 9. A cylinder head gasketincluding a pair of gasket baseplates held sandwiched between a cylinderhead and a cylinder block and having a combustion opening formed thereinin alignment with a cylinder bore, a spacer disposed around the cylinderbore to surround the cylinder bore in an endless manner, said spacerbeing held sandwiched between said pair of gasket baseplates, and a fullbead and a half bead formed on each of said pair of gasket baseplates ina region overlapped by said spacer,wherein the improvement comprisessaid full bead and said half bead extending continuously, completelyaround the circumference of the cylinder bore, the spacer as well as thefull bead and the half bead on each gasket baseplate being continuouslyheld sandwiched between the cylinder head and the cylinder block alongthe circumference of the cylinder bore, said half bead being positionedradially outwardly of said full bead.
 10. A cylinder head gasket for usebetween a cylinder head and a cylinder block having a cylinder bore, thecylinder head gasket comprising:a pair of gasket baseplates adapted tobe sandwiched between a cylinder head and a cylinder block, said gasketbaseplates having an opening formed therein for alignment with acylinder bore; an endless spacer adapted to be disposed around andsurround a cylinder bore, said spacer being sandwiched between said pairof gasket baseplates, said gasket baseplates each having a full bead anda half bead formed thereon in a region overlapping said spacer, saidfull bead and said half bead extending along said endless spacer andbeing adapted to extend continuously completely around the periphery ofsaid opening, said spacer and said full bead and said half bead in eachgasket baseplate being continuously circumferentially stacked andadapted to be in turn held between a cylinder head and a cylinder blockcontinuously along the circumference of a cylinder bore; and areinforcing plate of a reduced thickness, which is less than thethickness of said spacer, said reinforcing plate being disposed outboardof said spacer, said reinforcing plate being held sandwiched betweensaid pair of gasket baseplates.
 11. A cylinder head gasket for usebetween a cylinder head and a cylinder block having a cylinder bore, thecylinder head gasket comprising:a pair of gasket baseplates adapted tobe sandwiched between a cylinder head and a cylinder block, said gasketbaseplates having an opening formed therein for alignment with acylinder bore; an endless spacer adapted to be disposed around andsurround a cylinder bore, said spacer being sandwiched between said pairof gasket baseplates, said gasket baseplates each having a full bead anda half bead formed thereon in a region overlapping said spacer, saidfull bead and said half bead extending along said endless spacer andbeing adapted to extend continuously completely around the periphery ofsaid opening, said spacer and said full bead and said half bead in eachgasket baseplate being continuously circumferentially stacked andadapted to be in turn held between a cylinder head and a cylinder blockcontinuously along the circumference of a cylinder bore, said full beadbeing directly adjacent said opening formed in said gasket baseplate andhaving a central portion extending axially away from said spacer.
 12. Acylinder head gasket according to claim 11, wherein said half beadextends axially away from said spacer and is positioned radiallyoutwardly from said full bead.
 13. A cylinder head gasket for usebetween a cylinder head and a cylinder block having a cylinder bore, thecylinder head gasket comprising:a pair of gasket baseplates adapted tobe sandwiched between a cylinder head and a cylinder block, said gasketbaseplates having an opening formed therein for alignment with acylinder bore; an endless spacer adapted to be disposed around andsurround a cylinder bore, said spacer being sandwiched between said pairof gasket baseplates, said gasket baseplates each having a full bead anda half bead formed thereon in a region overlapping said spacer, saidfull bead and said half bead extending along said endless spacer andadapted to extend continuously completely around the periphery of saidopening, said spacer and said full bead and said half bead in eachgasket baseplate being continuously circumferentially stacked andadapted to be in turn held between a cylinder head and a cylinder blockcontinuously along the circumference of a cylinder bore, said half beadbeing positioned radially outwardly of said full bead.